1. Field of the Invention
This invention relates to an image processing apparatus and an endoscope image sensing and processing apparatus that subjects image signals to a predetermined calculating process to display, by different display methods, a portion outside a predetermined range of a subject quantity and a portion within the predetermined range of the subject quantity and an image processing method for performing different displays depending upon the subject quantity.
2. Description of the Related Art
Recently, an endoscope has been widely used which comprises an elongated insertion portion to be inserted into the coelom to observe the internal organ in the coelom or the like and/or which is able to perform a variety of curing treatments by using a treatment tool inserted into a treatment channel.
An endoscope apparatus of the foregoing type has been adapted to a variety of image processes in recent years. In order to enable an image process of the foregoing type to clearly separate an ineffective region, such as halation, and a dark portion and effective region from each other, a technology has been disclosed in, for example, Japanese Patent Laid-Open No. 2-268722 in which a portion encountered halation is detected and the foregoing region is displayed in such a manner that the foregoing region can be distinguished from the effective region.
As disclosed in Japanese Patent Laid-Open No. 3-21186, a technology has been disclosed which has an arrangement that the ineffective region exemplified by halation and a dark portion and the effective regions are clearly distinguished from each other at the time of displaying the image.
Hitherto, the processed image of the foregoing type has been displayed in such a manner that the ineffective regions exemplified by halation and the dark portion are clearly distinguished from each other. If the distribution of the quantities of hemoglobin is subjected to a pseudo color process in such a way that a subject range (hereinafter called a "subject level range") is set in accordance with the quantity of hemoglobin, no special attention has not been paid to pixels outside the subject level.
Therefore, the pixels outside the subject level range have been usually displayed in the same color as that for the maximum value of the subject level range if the pixels are higher than the subject level range and in the same color as that for the minimum value of the subject level range if the pixels are lower than the subject level range. If attention is paid to the color adjacent to the maximum value or that adjacent to the minimum value, it is difficult to distinguish whether the pixels are present outside the subject level range or adjacent to the maximum value of the subject level range or adjacent to the minimum value.
A conventional fiber scope sometimes encounters difficulty when change in the physically changed portion caused by a disease and that in the mucous membrane are observed. However, it is known that detection of the distribution of the degrees of oxygen saturation of hemoglobin in the blood will be helpful in early discovery of the physically changed portion caused by a disease.
As a method of measuring the degree of oxygen saturation of hemoglobin in the blood, a method is well-known in which the difference between absorption at wavelengths, for example 569 nm and 586 nm, at which the absorbance cannot be changed due to change in the degree of oxygen saturation and absorption at a wavelength, for example 577 nm, at which the same is considerably changed due to the change in the degree of oxygen saturation is used to measure the change in the degree of oxygen saturation in the mucous membrane.
As a method of obtaining information about the degree of oxygen saturation, an endoscope apparatus has been disclosed in, for example, Japanese Patent Laid-Open No. 63-311937 or Japanese Patent Laid-Open No. 1-280442 in which a narrow band filter of the foregoing wavelength is used to obtain the information about the degree of oxygen saturation.
However, in a conventional endoscope apparatus, obtaining the image of the degree of oxygen saturation includes a narrow band filter and undesirably forms an image in a color tone which is different from an image obtained from a usual visual observation when the image of the degree of oxygen saturation is being displayed. Since the image of the degree of oxygen saturation cannot express a fine change in the color of the mucous membrane, there arise a necessity of switching the image to a visible observation image.
In addition to the foregoing image processing apparatus adapted to the quantity of hemoglobin, there has been an image processing apparatus capable of visualizing the distribution of the concentrations of fluorochrome or that of ICG (Indocyanine Green) from the endoscope image. It is desirable to enable the image processing apparatus of the foregoing type to distinguish the portion having the value of the concentration of the fluorochrome or the value of the concentration of the ICG which is required by an observer to observe from the residual portions. However, the conventional image processing apparatus cannot easily enable the portion required to be observed to be discriminated in the image of the distribution of the concentrations of the fluorescence or the image of the distribution of the concentrations of the ICG or the intensified image, each of which is the processed image.
In a case of an image obtained by pseudo-color processing an image of the distribution of the concentrations of the fluorochrome or an image of the distribution of the concentrations of the ICG, the image is displayed in such a manner that the color is changed depending upon the value of the concentration of the fluorochrome or that of the ICG. However, the region of the concentration of the fluorochrome or that of the ICG required by the observer to observe cannot be distinguished in the image even if a color bar is displayed on the side portion of the image in order to make the value of the concentrations of the fluorochrome or that of the ICG to correspond to the display colors because the color change takes smoothly.
What is worse, the concentration of the fluorochrome or that of the ICG can be discriminated qualitatively in the image in which the concentration of the fluorochrome or that of the ICG is intensified. However, the concentrations cannot be quantitatively discriminated.